FIG. 8(A) schematically shows a specimen insertion device which is used with an electron microscope having X-ray analysis capability and inserts a specimen from a direction perpendicular to the optical axis Z. A specimen stage 1 has an opening 2 as shown in FIG. 8(B). The specimen, indicated by 3, is placed on the specimen-holding portion 7 of the specimen stage 1. An upper magnetic pole piece 4 and a lower magnetic pole piece 5 together form an objective lens. An X-ray detector 6 detects X-rays emitted from the specimen 3 when it is irradiated with the electron beam.
In the electron microscope of this construction, the specimen stage 1 is inserted from the direction perpendicular to the optical axis Z to observe the specimen 3. Then, the electron beam emitted by the electron gun (not shown) is directed toward the specimen 3. Electrons transmitted through the specimen 3 are magnified by lenses (not shown) located below the specimen 3. The magnified electron image is focused onto the fluorescent screen (not shown).
To make X-ray analysis of the specimen 3, the X-rays produced from the specimen 3 illuminated by the electron beam are detected by the aforementioned X-ray detector 6. The output signal from the detector 6 is sent to an X-ray analysis system (not shown), for performing the X-ray analysis.
The specimen stage 1 is generally made of a light element producing a very small amount of X-rays such as beryllium to reduce the X-ray emission from the specimen stage 1 in response to the illumination of the electron beam when the beam produced by the electron gun (not shown) leaks around the specimen-holding portion 7 of the stage 1. Therefore, most of the X-rays detected by the x-ray detector 6 are released from the specimen. Hence, the x-ray analysis can be performed accurately.
To improve the resolution of the electron microscope, the gap between the pole pieces 4 and 5 is made very small. Consequently, the specimen stage 1 is made very thin. An electron microscope having such thin specimen stage is disclosed in U.S. Pat. No. 4,596,934. While the primary electrons are penetrating the specimen 3, the electrons are scattered. Some of the scattered electrons collide against the lower magnetic pole piece 5, so that X-rays are produced from this pole piece.
Since the specimen stage is made of a light element and thin as described above, the X-rays emanating from the lower pole piece penetrate the specimen stage 1. The X-rays transmitted through the stage 1 are detected by the X-ray detector 6 in the same way as the X-rays emitted form the specimen. In consequence, it is impossible to make accurate X-ray analysis of the specimen.